Retractable boring arm assembly for mining machine



June 28, 1955 J. s. ROBBINS ET AL {711,887

RETRACTABLE BORING ARM ASSEMBLY FOR MINING MACHINE Filed Oct. 13, 1953 2 Sheets-Sheet l INVENTORS JAMES 5. ROBBINS BY CARL A- W\LN\5 4 W W ATTORNEY June 28, 1955 J, 5, ROBBINS ET AL RETRACTABLE BORING ARM ASSEMBLY FOR MINING MACHINE 2 Sheets-Sheet 2 Filed Oct. 15, 1953 FIG. 4

INVENTORS JAME6 5- ROEJUNS CARL A. W\LN\6 Z TTORNEY RETRACTABLE BORING ARM ASSEMBLY FOR MINING MACHINE James S. Robbins and Carl A. Wilms, Chicago, 11]., as-

signors to Goodman Manufacturing Company, Chicago, Ill a corporation of Illinois Application October 13, 1953, Serial No. 385,849

4 Claims. (Cl. 262- -7) This invention relates to improvements in mining machines of the boring type, wherein at least two boring heads, each having radial arms with forwardly projecting cutter bits, are arranged in side-by-side relation to cut two contiguous bores in advance of the machine. Machines of the general type above mentioned are commonly known as McKinlay miners.

It is highly advantageous to provide means for extending or retracting the effective cutting length of the radial arms, in accordance with the height of the coal seam to be cut, and also aid during tramming the machine when it is often desirable to reduce the outermost cutters at some diameter less than their normal working diameter. Thus, for best operation, it is best to provide the greatest possible variation between maximum and minimum working positions, consistent with maintaining the necessary strength of the parts, because clearance requirements may often be measured in terms of inches or fractions thereof.

Among the objects of the present invention is to provide an improved and simplified construction for a boring head for expanding or retracting, in unison, the ends of the radial cutter arms.

A further object is to provide an improved construction of the kind memtioned, utilizing an umbrella type of expansion linkage, and aifording anincreased variation between the maximum and minimum working diameters of the boring arms.

A still further object of the invention is to provide an improved and simplified means for assembling the parts of the cutter head, including the tapered nose at the outer end of the main drive shaft of the head.

Other objects and advantages of the invention will appear from time to time as the following description proceeds.

The invention may best be understood by reference to the accompanying drawings, in which:

Figure l is a longitudinal fragmentary section of a boring head assembly, made in accordance with our invention, with some parts broken away or omitted;

Figure 2 is a fragmentary section taken on line 22 of Figure 1;

Figure 3 is a detail section taken on line 3-3 of Figure 1;

Figure 4 is a detail section taken on line 44 of Figure 1, with certain parts omitted.

Referring to details of the embodiment of our invention illustrated in the drawings, the same is shown as applied to a single boring head, indicated generally at it which, in the form shown, has three radial boring arms arranged at equal angles of 120 degrees to each other, one of which is shown in Figure 1. The general structure and arrangement of mining machines of the boring type, with extensible radial arms, is well known in the art, so detailed description of the main parts of the machine is unnecessary for the understanding of the present invention, excepting as to such parts which are associated with a single boring head shown in the drawings.

nited States Patent ice The boring head It is mounted at the front end of a suitable mobile frame (not shown) including a housing 12 having a forwardly projecting, generally cylindrical, hollow shaft 13 journalled in rear bearings 14 and front bearings 15.

A hub 16 is keyed at 16b on the front end of shaft 13 and has a reduced bore 16a at its rear end abutting the inner race 15a of the front bearing 15. Said inner race in turn abuts a shoulder 15b on shaft 13. The hub 16 has a plurality (herein three) of hollow radial arm portions 17 formed integrally therewith.

Each of the arm portions 17 has a movable end portion 18, with its inner end consisting of a radial slide 18a, telescopically fitting in the end of its arm portion for extension or retraction. In the form shown herein, the radial slides 18a are generally cylindrical in cross section, as seen in Figure 2, and are splined at 19, 19 within the bores 20 of the arm portions.

Each radial arm portion 17 carries one or more forwardly projecting cutter bit supports 21 having suitable cutter bits 22 along their outer ends in the usual manner for cutting circular kerfs in the working face. The outer end of each telescopic portion 18 has a similar forwardly projecting cutter bit support 23 with cutter bits 23a thereon for cutting the outermost kerf.

A tapered nose 24, having cutter bits 25 at its front end, is secured to the center of the hub 16 and encloses the front end of the latter. As shown in Figure 1, the rear end of said nose is formed, as usual, with a spiral rib 26 on its exterior. Said nose is hollow and has an annular rear end portion 27 fitting in an enlarged bore 28 formed in the front end of the hub. The nose is secured to the hub by bolts 29, 29 passing through a flange 30. A center bearing 31 is also formed integrally within the nose and projects rearwardly therefrom, for a purpose to be hereinafter described.

Referring now to the mechanism for extending or retracting the telescopic end portions 18 of the radial arms, it will be seen from Figure 1 that the main shaft 13 has a bore 32 at its front end, in which is fitted a generally cylindrical, axially movable slide 33. Said slide has the inner ends of umbrella type links 34, 34 pivoted on pins 34a, 340: at the front end thereof. The outer ends of links 34 are pivoted on pins 34b, 34b intermediate the ends of each of the telescopic radial slides 18a. The radial slides 18a have cut-away slots 18b near their inner ends to permit the links 34 to assume a rearwardly and inwardly inclined angle in their contracted position. The adjacent rear wall of the hub is formed with outwardly bowed portions 160 to afford similar clearance for said links.

Axially aligned with the shaft 13, but fixed at it rear end to the frame housing 12, is a hydraulic cylinder 35, herein consisting of an outer shell 36 and an inner shell 37. Said inner shell has a piston 38 therein, with a piston rod 39 extending forwardly and connected to the slide 33 through a rotatable connection, herein consisting of a two-way thrust bearing assembly 40 of conventional construction, carried in a retaining plate 41 secured to the rear end of said slide as by bolts 42.

The cylinder 35' is double-acting; in the form shown, fluid pressure is admitted through line 43 and bore 44 to the rear end of the cylinder and through line 45 communicating with the space within the cylinder shells 36 and 37 to inlets 46 at the front end of the cylinder. Fluid pressure is supplied from a suitable source under manual valve control (not shown).

The main shaft 13 has a spur gear 47 splined thereon, and driven through a pinion 48 on shaft 49 from a suitable source of power, to rotate the boring head.

Referring now more particularly to the construction of the slide 33 and its associated parts, it will be observed from Figure 1 that the front end of the main drive shaft 13 terminates a considerable distance short of the front end of the hub 16, and the axial slide 33 is arranged to project beyond the front end of the bore 32 in the drive shaft in the fully expanded position of the arms, as shown in full lines in this figure. The purpose of this construction is to permit the movable end portions 18 to be retracted inwardly without interference by the main shaft, thus affording the maximum degree of contraction of the end portions, as indicated in dotted lines in Figure 1.

The axial slide is provided at its front end with a cylindrical guide rod 50 slidably engaged in the center bearing 31, previously mentioned as formed in the rear end of the tapered nose 24. This bearing thus affords sliding support for the front end of the axial slide 33 in all positions of the latter, particularly when said slide is partially extended beyond the front end of the bore 32.

The hub 16 is held in place against the front end of the main shaft bearing 15 by a plurality of segmental keeper plates 51, 51, herein three in number as shown in Figure 4. Each of said keeper plates is disposed between a pair of adjacent umbrella links 34. They are secured to the end face of the hollow main shaft by bolts 52, with their outer edges engaged with an outwardly facing shoulder 53 defining the inner end of the enlarged bore 28 in the hub 16. The keeper plates 51 are also disposed rearwardly of the paths of movement of the radial slides 18a of the extensible arm portions 18, so that they do not limit the inward movement of said arm portions.

. As a further feature of our present invention, it will be observed from Figure 1 that, when the radial slides 18a are in the fully extended position shown in full lines in this figure, the umbrella links 34 are in dead-center or straight line position between the axial slide 33 and each of the radial slides. In this position, there is a clearance afforded between the front face 55 of the axial slide and the rear face of the center bearing 31 in the nose 24, which permits the slide to be moved slightly beyond the dead-center position of the links so that they will stay in this stable over-center condition during mining, so that it is unnecessary to rely upon a constant hydraulic pressure to maintain the movable arm portions 18 in their fully extended positions.

Although we have shown and described certain embodiments of our invention, it will be understood that we do not wish to be limited to the exact construction shown and described, but that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

We claim:

1. In a mining machine including a frame, a hollow drive shaft journalled in said frame, a boring head on said drive shaft having a hollow hub and a plurality of radially extending cutter-carrying boring arms, said arms having cutter-carrying end portions telescopically mounted therein, a slide movable axially of said drive shaft, means for reciprocating said slide, links pivotally connected between said slide and each of said telescopic end portions, the hollow hub having a bore at its front end within which the outer end of the drive shaft is keyed, and means for securing said hub on said shaft including a plurality of circumferentially spaced keeper plates fixed to the outer end of said shaft intermediate the paths of movement of said links and rearwardly of the paths of movement of said telescopic end portions, and the hub having a rearwardly facing shoulder engageable by the outer edges of said keeper plates.

2. A mining machine structure in accordance with claim 1, wherein the hollow hub has an axially disposed bearing fixed at its front end, and the slide has a guide rod projecting from its front end slidably supported in said axial bearing.

3. A mining machine structure in accordance with claim 2, wherein the axially disposed bearing forms part of a hollow tapered nose fixed to and projecting axially from the front end of said hub.

4. A mining machine structure in accordance with claim 3, wherein the tapered nose has an annular rear end portion fitting in the front end of the hub, and a flange surrounds said rear end portion and is bolted to the front face of said hub.

References Cited in the file of this patent UNITED STATES PATENTS 241,483 Faught May 17, 1881 314,926 Freidel et al. Mar. 31, 1885 1,335,723 Campbell I Apr. 6, 1920 1,371,224 Campbell Mar. 15, 1921 1,603,621 McKinlay Oct. 19, 1926 1,726,963 McKinlay Sept. 3, 1929 2,081,842 Sharp May 25, 1937 OTHER REFERENCES Coal Age, May 13, 1926, pp. 667-670. 

